URD Cable Rehabilitation Program

1. URD Cable Rehabilitation Program SWEDE 2009 Tulsa, OK May 7, 2009 B. Shawn Cobb, P.E.

2. Presentation Objective • Update on URD System Performance • URD System History • URD System & Performance Statistics • Current Status • Action Plan • Answer Questions

3. What is a URD System? • Underground Residential Distribution • Single-phase underground electric distribution system • Provides electric service to residential customers in subdivisions • Typically utilizes a loop feed design (two sources) feeding many sections of cables in between transformers

4. URD System History • 1939 – Earliest URD system in Danvers Subdivision • 1964 – Installed first direct-buried URD systems • 1984 – Initiated a cable replacement program based on failure rate • 1986 – Began installing cable in conduit for new URD primary cable installations • 1993 – Cable injection was introduced for 13kV cables • 1999 – Cable injection was developed for 35 kV cables

5. URD System&Performance Statistics

6. Direct-buried URD • The total amount of direct-buried URD cable installed between 1964 and 1986 is 1,628 miles • The oldest remaining direct-buried cable is 38 years old • Direct-buried URD cable was not performing well (high failure rates), so a cable rehabilitation program was initiated in 1984.

7. URD Direct-buried Cable

8. URD Direct-buried Cable

9. URD Direct-buried Cable

10. URD Direct-buried Cable

11. URD Direct-buried Cable

12. URD Direct-buried Cable

13. URD Direct-buried System Failures

14. URD Direct-buried System Failures

15. URD Direct-buried System Failures

16. URD Direct-buried System Failures

17. URD Direct-buried System Failures

18. URD Direct-buried System Failures

19. URD Direct-buried System Failures

20. URD Direct-buried System Failures

21. URD Direct-buried System Failures

22. URD Direct-buried System Failures

23. URD Direct-buried System Failures

24. Current Status • Through the Cable Rehabilitation Program, we have replaced 884 miles of direct-buried cable with cable in conduit and have injected 251 miles with the injection process. This leaves us with 493 miles of direct-buried cable that still need to be addressed. • The current contractor cost to replace direct-buried cable with cable in conduit is $160,000 per mile. • The current cost for cable injection is $75,000 per mile.

25. Action Plan • With an annual budget of $4.5 Million, the recommendation is to continue replacing direct-buried cable with cable in conduit and injecting cable with silicon. The proposed plan is to replace 15 miles with cable in conduit and to inject 30 miles. 1. This recommendation will maximize the use of our annual budget. 2. Cable injection will address and reduce our cable failure rate. 3. Cable replacement will address and reduce transformer failures. 4. Injection contractor has one full time crew which maximizes their efficiency and productivity by injecting 30 miles of direct-buried cable per year.

26. Proposed Plan (cont) • At a rate of 45 miles per year, it will take approximately 11 years to rehabilitate all of the remaining direct buried cable. At the completion of the program, there will be about 390 miles of injected cables. The remainder will be cable in conduit. • The recommendation was not based solely on financial calculations. The cable replacement also addresses the transformers, while the cable injection process does not.

27. Questions?